1. Field of the Invention
This invention relates generally to diapers and more particularly, to an improved disposable diaper having fluid traps along the side edges thereof.
2. DESCRIPTION OF THE PRIOR ART
Conventional disposable diapers comprise a rectangular back sheet of waterproof material, a rectangular absorbent pad and a rectangular top sheet of hydrophobic material. The back sheet is generally wider than the pad and the top or face sheet and the longitudinal edges of the back sheet extend past the longitudinal edges of the pad and the face sheet. The back sheet is folded around the edges of the pad and onto the face sheet forming side flaps. The longitudinal edges of the back sheet are then adhered to the face sheet.
In order to successfully meet consumer expectations a disposable diaper must, as an assembly, have sufficient strength to prevent tearing when applied and when worn by an infant and must also have sufficient limpness or ability to be molded or adjusted by hand to fit closely around the thighs and trunk of an infant. This limpness, or ability to be molded or adjusted by hand, is required in order to create a seal to contain discharged urine in order to give the absorbent pad sufficient time to absorb the urine. Failure to provide these features results in a product which causes soiled clothing, infant discomfort and a general adverse reaction on the part of the consumer.
Present disposable diapers attempt to meet the above goal of having sufficient strength to avoid tearing by providing the above mentioned folded edge of back sheet on each of the longitudinal edges of the diaper. The back sheet on one form of conventional disposable diaper has side flaps which are folded, one each, around the longitudinal edges of the absorbent pad and are fastened to the face sheet by adhesive means. In this form of conventional disposable diaper the combined width of the side flaps are equal to approximately two thirds of the overall width of the diaper in the folded configuration. The side flaps are placed in a complex state of combined bending and tensile stress when the conventional disposable diaper is applied. This results in local buckling and bulging of the back sheet away from the thighs and trunk of the infant with consequent loss of sealing contact.
Another disadvantage of present conventional disposable diapers is that the folding of the back sheet over the edge of the absorbent pad prevents air from contacting the edge of the pad. The consequent thermal insulation of the edges of the pad by the back sheet contributes to the absorbent pad retaining the heat produced by the absorption and accumulation of waste products and also retaining body heat. This heat retaining property of conventional disposable diapers is undesirable since it leads to infant discomfort. In addition to the undesirable effects in conventional disposable diapers related to the side flaps which cover the longitudinal edges of the pad, additional undesireable effects are related to the side flap portions which overlay the face sheet. These portions of the backsheet contribute to the undesirable thermal insulating properties of the conventional disposable diaper. In addition, when the conventional diposable diaper is applied to an infant, the side flap portions which overlay the face sheet form a relatively large portion of the overall width of the diaper in the narrow crotch area. The side flap portions prevent absorption of waste products through the hydrophobic face sheet in those covered areas and actually increase dripping of excess fluid. In addition, in the crotch area, those portions of the back sheet which overlay the face sheet, since they form a relatively large portion of the overall disposable diaper width, readily become wet with urine and cause infant discomfort. In certain cases these wet portions at the edges of the side flaps in contact with the infant's skin can lead to skin rashes and other skin disorders caused by the combined effects of urine and body heat.
A rectangular diaper is disclosed in the U.S. Pat. No. 3,592,194, issued to Robert C. Duncan on July 13, 1971 for DIAPER HAVING IMPROVED WICKING AND DRYNESS. This rectangular diaper is folded in a box pleat such as also disclosed in British Pat. No. 1,011,888 of Dec. 1, 1965.
An object of the invention is to provide a more comfortable and better fitting diaper in which the wicking of fluids is enhanced and a fluid seal is provided.
An additional object of this invention is to provide a disposable diaper having relatively high tensile strength in the longitudinal direction combined with relatively low transverse bending strength.
Another object of this invention is to provide a disposable diaper having increased flexibility of the longitudinal edges or side thereof to facilitate the formation of a desirable tight fit to the leg and trunk of an infant.
A further object of this invention resides in the provision of a disposable diaper having a pair of fluid traps spaced inwardly of the longitudinal edges for increased sealing capability.